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| Home > Publications database > Herstellung von Hochtemperatur-Brennstoffzellen über physikalische Gasphasenabscheidung |
| Dissertation / PhD Thesis/Book | PreJuSER-3001 |
2008
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-89336-565-4
Please use a persistent id in citations: http://hdl.handle.net/2128/3618
Abstract: Solide oxide fuel cells (SOFC) are very efficient devices which help to gain electricity from chemical energy. In order to launch SOFC successfully, the production costs have to be reduced and a sufficient long-term stability as well as the reliability of the different system components have to be guaranteed. This can be achieved by lowering the operating temperature to 600-700°C. If the construction (development) retained unchanged, the reduced temperature would, however, cause an increase of the cell resistance, which would, as a consequence, result in a lower performance. During this work (experiment) the physical vapor deposition (PVD) for the production of thin tight layers was adopted to enable an increase of performance of SOFC in case of low temperatures. The first part of this work was focused on coating diffusion barriers to avoid the reaction between the cathode and electrolyte materials. The second part was focused on the development of an electrolyte composite to minimize the contribution of the electrolyte resistance to the cell. Two PVD methods were analysed for the seperation of thin layers: electron beam physical vapor deposition (EB-PVD) and reactive sputtering. The performance of cells with a diffusion barrier, which were manufactured via PVD, was more than 50% higher than the performance of cells with a diffusion barrier, which were manufactured via screen printing. Long-term measurements show that SOFCs with PVD diffusion barriers have a higher performance as well as a lower increase of the cell resistance in comparison to cells with a diffusion barrier manufacured by screen printing with a sintering step. In case of operating temperatures lower than 700°C the electrolyte resistance plays an important role for the complete cell resistance, so that a further increase of performance requires thinner electrolyte layers. Especially in case of PVD- methods, it is very difficult to deposit a gastight electrolyte layer on a porous substrate. Consequently, it is important to condition the surface of the porous substrate first, so that there are no defects left, which are bigger than the electrolyte layer to be applicated. It was possible to manufacture an electrolyte layer out of a composite manufactured by PVD, so that a passable leakage for the SOFC application could be achieved due to a suitable material selection and a layer thickness respectively. The performance of cells with an electrolyte composite manufactured by PVD is 0,93 A/cm$^{2}$ at 650°C and 0,7 V whereas the the performance of cells with an electrolyte manufactured by vacuum slip casting with a sintering step is 0,64 A/cm$^{2}$ at 650°C and 0,7V. That means a performance improvement of about 40%.
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